The present invention relates to apparatus for cooling apparatus and, in particular to a dehumidification and cooling system employing synergistic effects of serially coupled direct expansion (xe2x80x9cDXxe2x80x9d) and liquid chilling to achieve low air stream dew points with low power consumption under conditions of high moisture loads.
The cooling systems commercial and retail facilities generally include a remotely located primary unit that is individually connected to various cooling loads or zones, such as air conditioning. Chilled liquid or direct expansion cooling systems are typically used.
Evolving standards and regulations are requiring increased outdoor air introduction into commercial and industrial buildings for improving interior air quality. Introducing such outdoor air: into areas having stringent humidity control requirements can greatly increase of dehumidification removal load requirements, particularly during periods of increased temperature and humidity. Humidity sensitive environments such as supermarkets, libraries, sports arenas, hotels, food storage, and process control areas can suffer severe adverse operational problems, from mold, mildew, and product and equipment damage if the cooling systems cannot handle the increased moisture. To adequately handle moisture removal in such situations, it has been widely accepted that an internal dew point temperature of 50xc2x0 F. or less is required in these spaces, and that the supply air accordingly must be about 40xc2x0 F. At such lowered temperature, traditional direct expansion dehumidifiers are prone to icing, and supplemental defrost systems are required. The additional costs associated with the defrost systems and the attendant operational problems have reduced the use of direct expansion dehumidification systems in these humidity dependent applications.
The lower dew points can be achieved without defrost cycles using chilled liquid systems, enabling operational dew points as low as about 34xc2x0 F. Sophisticated controls systems, however, are required and the power consumption is greater than the direct expansion systems. Alternatively, desiccant dehumidifiers may be used to achieve these requisite dew point conditions, but only at high operational and maintenance costs.
The present invention provides a multiple stage dehumidification and cooling system wherein a first stage direct expansion dehumidifier operating at its optimum dew point to an entering high humidity, high temperature air stream and effecting a first lowering of the temperature and humidity of the air stream, with the conditioned air stream being serially conveyed to a second stage chilled liquid dehumidifier operating at its optimum dew point and effecting a second lowering of the temperature and humidity, and thereafter to a third stage reheat coil for providing an exiting air stream of desired temperature and humidity conditioning. The synergistic coupling provides significant power saving over the prior alternatives of desiccant and chilled liquid systems. Further, the stages are individually modulated to reduce power consumptions as the load temperature and humidity set points are approached.